The invention relates to an arrangement for coupling optical waveguides to an optical device, particularly for a laser application, the optical waveguide being held in a fiber plug which can be connected with a countercoupling part of the optical device and being bared on its end which is to be introduced into the countercoupling part, and having a centering unit for the optical waveguide.
When coupling laser beams into optical waveguides--and correspondingly for connecting two optical waveguides--it is important align the optical axes of the optical waveguide and of the laser beam. Deviations from center positions result in power losses and, in the case of higher laser powers, may even lead to the destruction of the optical waveguide. In the case of the known couplings and plug-type connections for optical waveguides, the deviation of the alignment of the optical waveguide with respect to the given optical axis of the laser beam or of another optical waveguide is influenced by a plurality of mechanical tolerances at the plug-type connectors, such as the inside diameter of the coupling sleeve, the outside diameter of the plug, the inside diameter and the conical form of the plug bore, the outside diameter and the concentricity of the optical waveguides, and the like. The low permissible mechanical tolerances for optical waveguide plugs are important factors for the manufacturing methods and the relatively high prices of the previous coupling arrangements.
German Patent Document DE 42 01 769 C1 describes a coupling arrangement of initially mentioned type in which the centering unit is constructed such that the centering sleeve is on the fiber plug itself. When this fiber plug is now introduced into the optical device and "centered", only an extremely poor centering can be achieved in this case because of the different given tolerances. These tolerances may exist between the outside diameter of the plug pin and of the plug socket, the inside diameter and the outside diameter of the plug pin, between the plug pin and the shown supporting body, between the bore in the supporting body and the fiber passing through and may consist of concentricity tolerances of the bore in the supporting body. The cumulative effect of these tolerances no longer permits a precise adjustment which has the result that only an insufficient coupling-in is achieved. In an extreme case, the laser spot may even be focused beside to the fiber.
It is therefore an object of the invention to construct a coupling arrangement for optical waveguides, particularly for the coupling to laser systems, such that it can be manufactured at low cost and nevertheless with a very high coupling quality so that, predominantly in the medical field, it is suitable to be used as a throw-away plug, which is absolutely required, for example, for body probes , which may not be used more than once.
For achieving this object, it is provided according to the invention that the centering unit is arranged in the countercoupling part and comprises a centering sleeve which is aligned flush with respect to the optical axis of the adjoining optical device. The centering unit is fixedly connected with the countercoupling part, and when the fiber plug is plugged into the countercoupling part, the fiber is introduced into the centering sleeve in which it is centered.
The invention takes into account the fact that only the plug with the connecting optical waveguide is required to be discarded whereas, with respect to the countercoupling part which establishes the connection either to another optical waveguide (which must not be discarded) or to the laser system of a medical instrument, it is not important that an optically precise alignment with the centering unit is carried out here at high expenditures. The mechanical tolerances are reduced to those of the optical waveguide bore in the plug-in socket and the diameter as well as the concentricity of the fiber. All other tolerances, as those mentioned above, play no role for the optical alignment; that is, the tolerances with which the plug is held in the coupling part do not cumulate to the tolerances to be minimized with ordinary expenditures which exist between the diameter of the optical waveguide bore of the centering sleeve and the diameter as well as the concentricity of the optical waveguide fiber.
According to another embodiment of the invention, the only existing tolerance which becomes noticeable as an alignment error can be reduced by providing a centering sleeve which is elastic in its diameter, and is, for example, slotted or constructed of an inherently elastic material. As a result, the mentioned tolerance can virtually be reduced to zero.
The compensation between the tolerances existing between the fiber plug and the countercoupling part, which according to the invention need not specifically be taken into account, is obtained by the elastic bendability of the fiber of the optical waveguide which projects toward the front over the plug . For introducing this fiber into the centering sleeve, the latter is preferably provided with an introducing cone. The end to be introduced into the countercoupling part of the optical waveguide can be bared down to the optical fiber cladding.
As demonstrated, the coupling arrangement according to the invention can also be used for connecting two optical waveguides, in which case a countercoupling part equipped with two plug receiving devices situated and aligned opposite one another and with a centering unit is used for receiving their two optical waveguide fibers.
The fiber plugs can be fastened on the countercoupling part by means of instant plug-in connection. All kinds of different instant plug-in connections are suitable for this purpose which have already been developed for electric plug-type connections, for example, plug-type connections having a ball-type latch and an outer spring-loaded screw cap, as frequently used, for example, during the quick-action chucking of drills.
The optical waveguide can be connected with the fiber plug with low precision requirements by means of shrinking-on, chucking, gluing or injection molding on the elastic fiber cladding of the optical waveguide. As a result, the costs for producing such optical waveguides with the fiber plug as a disposable article can be minimized.
In this case, it is naturally still within the scope of the invention to provide the fiber projecting out of the front side of the fiber plug, in a required length, by means of optical processing or breaking, with the required light entry surface.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.